1. Field of the Invention
The present invention relates to an apparatus for determining thermomechanical properties of a photo-sensitive material during exposure to light.
2. Description of the Related Art
Modern production and manufacturing processes require that materials be characterized with respect to physical properties such as glass transition, modulus (stiffness), thermal expansion, and shrinkage (during a cure, for example) to maximize the efficiency of the process and the consistency of the final product to meet required application specifications. Thermal analysis of materials involves various methods for measuring these and other physical and/or chemical properties of a material as a function of temperature. Instruments such as dynamic mechanical analyzers (DMAs) and thermomechanical analyzers (TMAs) may be used to obtain this information.

A typical prior art thermal analysis system is shown in FIGS. 7 and 8. A sample tube 1 has a sample holding area 3 at a bottom end of the sample tube. A sample 5 to be tested is mounted in the sample holding area 3 and a probe 7 is inserted through a top of the sample tube 1 to the sample area to perform a test on the sample 5. The specific configuration shown in FIG. 7 is a 3-point bending test configuration and the sample 5 is a bar. Instead of a bar, the geometry of the sample 5 may be that of a film, fiber, rod, cylinder, disk or liquid. Furthermore, instead of a 3-point bending configuration, the test configuration or measuring system may include 2- and 4-point bending, single and dual cantilever, film extension, fiber extension, or parallel plates. For all combinations of test configurations and samples, a force is applied to the sample 5 via the probe 7.
As shown in FIG. 8, the bottom end of the sample tube 1xe2x80x94i.e. the sample holding area 3xe2x80x94is inserted in a cavity 13 in a temperature control unit 9xe2x80x94i.e. a furnace or refrigeration unitxe2x80x94to control the temperature of the sample 5 during the characterization test. A split-ring ceramic insulator 11 is mounted around the sample tube 1 at the entrance area to the cavity 13 for closing the temperature control unit 9 during operation and for reducing heat loss and/or gain during its operation. FIG. 8 also shows a thermocouple 15 in the sample tube 1 and a locking nut 17 and locking mechanism 19 for holding the sample tube 1 in place during the test. The locking nut 17 and locking mechanism 19 are protected by a cover 21. A specific example of this type of instrument is a Perkin-Elmer DMA 7 Dynamic Mechanical Analyzer.
This prior art device operates very well for most samples. However, it is not possible to characterize the mechanical properties of a photo-sensitive material throughout its exposure to a light source, while accurately controlling temperature. The configuration of the temperature control unit prevents the illumination of the sample. Accordingly, a sample can not be illuminated in this prior art device while the sample tube is in the temperature control unit.
An apparatus for measuring thermomechanical properties of a photo-sensitive material sample during exposure to light such, for example, as during a photo-induced cure, according to the present invention, includes a sample holder having a sample support positionable in a sample holding area of the sample holder for holding the photo-sensitive material sample, a probe disposable relative to the sample support for measuring the thermomechanical properties of the photo-sensitive material sample, a temperature control unit having a cavity for receiving the sample holder and maintaining the sample holder within a controlled temperature range, and a lighting assembly operatively arranged for directing a light signal into the sample holder for illuminating the photo-sensitive material.
The lighting assembly may comprise a light source directed into a portal or other opening in the sample tube arranged at a location of the sample tube which is not insertable into the temperature control unit. Furthermore, a mirror or a light diffuser may be arranged in the sample tube to ensure that the sample is uniformly illuminated.
Alternatively, the lighting assembly may comprise a light source located in the temperature control unit.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.